Semiconductor alloy with spatially non-uniform change of composition close to the averaged value, corresponding to the transition between gapless and narrow-gap states, is studied. The density of states is calculated within the two-band model of band structure with random change of the position of the conduction band bottom and with a uniform valence band top. The appearance of an inhomogeneity-induced gap in the energy dependence of the density of states is discussed for the cases of short-range and long-range non-uniformities of composition. The peculiarities of the kinetic effects due to modification of the gapless state in such non-uniform semiconductors are discussed.